Low friction radial piston pump or motor



July M J. Teams 3,520,233

LOW FRICTION RADIAL PISTON PUMP OR MOTOR Filed Jan. 50, 1969 5Sheds-Sheet i July Wm J. TOBIAS 3,520,233

LOW FRICTION RADIAL PISTON PUMP OR MOTOR Filed Jan. 50, 1969 5Sheets-Shoot :3

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l.\'l'liN'l'i)R. JAROMIR roams July 14, QW .1. TOBIAS LOW FRICTIONRADIAL PISTON PUMP OR MOTOR Filed Jan. 30, 1969 5 Sheets-Sheet 5INVENTOR. JAROMIR TOBIAS COCOOE ATTORNEY United States Patent 3,520,233LOW FRICTION RADIAL PISTON PUMP OR MOTOR Jaromir Tobias, Box 141, RD. 2,Rhinebeck, N.Y. 12572 Continuation-impart of application Ser. No.751,801, Aug. 12, 1968. This application Jan. 30, 1969, Ser. No. 795,325

Int. Cl. F04b 1/10, 9/00, /00

US. Cl. 91-495 1 Claim ABSTRACT OF THE DISCLOSURE A radial piston pumpor motor including a cylinder block rotatable about a pintle shaft, areaction ring assembly rotatable about an axis parallel to and displacedfrom the axis of said pintle shaft, pistons reciprocable in the bores ofsaid cylinders and link means comprising at least one pair ofparallelogram links connecting the pistons to the reaction ring, fortransmitting forces be- H tween said assembly and pistons. Theconnection between the link means and piston is effected along a lineperpendicular to the piston axis, the assembly thus being characterizedby a force transmission between pistons and reaction ring whichprecludes the application to the pistons of forces which tend to cock ortilt the pistons relative to the cylinder bores.

This application is a continuation-in-part of my copending applicationSer. No. 751,801, filed Aug. 12, 1968, entitled Radial Piston Pump andMotor Device.

BACKGROUND OF THE INVENTION Field of the invention This invention is inthe field of radial piston pumps and motors.

The prior art It is well known to provide a radial piston pump or motorin which a block having radially directed cylinders rotates about apintle shaft. The pintle shaft includes outwardly directed high and lowpressure distribution chambers sequentially communicated to thecylinders as they rotate about the shaft by fluid passages extendingradially from the cylinders and opening onto the distribution chambers.

In the typical pump or motor of this type, a reaction ring surrounds thepistons and the outermost ends of the pistons, either directly orthrough an interposed piston shoe, are pressed against the reactionring. The axis of the reaction ring is displaced from the axis of thepintle shaft in normal operation and thus, in the course of rotation ofthe cylinder block, pressure is exerted by the pistons against reactionring portions which are not precisely perpendicular to the axes of thecylinder bores.

As a result of the application of such pressures againstnon-perpendicular portions of the reaction ring, it will be observedthat cocking or tilting force vectors are applied against the pistonmembers during substantially the entire rotation of the cylinder block,the forces being axial of the piston only when a projection of thecylinder axis simultaneously intersects the axes of the reaction ringand pintle shaft, i.e. at the innermost and outermost limits of movementof the pistons within the cylinders. As a result of the cocking ortilting forces applied to the piston which tend to tilt the piston in aplane extending through the axes of the cylinders, wear of the pistonand cylinder components is tremendously accelerated under load.

Various attempts have been made to counteract the effects of wear.Specifically, it has been proposed to elongate the pistons to thusreduce the deleterious effects of nonaxlally applied forces. However,piston elongation introduces other problems which materially detractfrom the elficiency and compactness of the pump or motor.

For example, where lengthwisely extended piston areas engage thecylinder bores, lubrication of the large, relatively moving surfaces isdifficult and expedients such as by-pass lubrication flow passages andthe like are indicated. Further, displacement per unit size is obviouslyadversely affected where large overlaps between the pistons and cylinderbores must be retained.

It will be observed that an increased piston stroke in hydraulic devicesof this sort is achieved by increasing the distance between the pintleaxis and the reaction ring axis and that the side components of forcesexerted increase with such displacement. Accordingly, wear of the partsis increased drastically with attempts to increase the piston stroke.

Other expedients have been employed to counteract the effects of pistoncocking. In US. Pat. No. 3,255,706, for instance, a complex arrangementis provided whereby fluid from the pressure chamber is diverted throughthe pistons and expelled into a chamber disposed between the cylinderwall and a side portion of the piston, the forces thus developed tendingto counteract the tilting tendencies of the piston. Such solutionprovides, at best, an inexact compensation since the correcting forcescan only roughly approximate the tilting forces. Also, the correctiveeffects can be achieved only with pistons traversing the pressuredistribution chamber.

Further, such apparatus must reduce the efficiency of the device bydrawing away significant quantities of the fluid under pressure.

SUMMARY OF THE INVENTION The present invention relates to a radialpiston pump or motor wherein the forces exerted between the pistons andthe reaction ring are channeled through a parallelogram link connectorassembly comprising a pair of relatively movable arms or links pivotallyconnected at spaced points to the piston assembly, which points arenormal to the axis of the cylinder bore. The other ends of the links areconnected to spaced points on the reaction ring.

The parallel links assure that at all positions of the block relative tothe reaction ring, the piston axis is maintained parallel with the axisof the cylinder and, thus, there is no cocking or tilting forces exertedon the piston.

The device above described may be, but is not necessarily, combined witha further refinement incorporating a piston stabilizer which functionsto prevent the piston axis, although maintained parallel with thecylinder axis by the link assembly, from tending to be displacedtransversely with respect to the cylinder axis. More specifically, theparallel link assembly prevents any cocking of the piston and thestabilizer assembly maintains the parallel oriented piston centralizedwithin the cylinder bore.

From the foregoing it will be readily appreciated that numerousadvantages flow from the use of the parallel link assembly per se or incombination with the above described refinements. Specifically, it ispossible to use a piston head which is shorter than heretoforepracticable, with resultant savings in mass, reduction in size, andelimination of lubrication problems.

Secondly, since no side forces in any significant amounts are exerted bythe piston against the cylinder, problems of wear between the piston andcylinder components are virtually eliminated.

The linkage also permits a far greater piston travel than heretoforepracticable, with little increase in overall Sue.

A further advantage lies in the fact that, since the engagement of thepiston within the cylinder is not relied on as the means for stabilizingthe piston, it is possible, for the first time in a hydraulic device ofthis type, to make effective use of piston rings, thus greatly reducingthe cost of fabrication by increasing permitted tolerances andfacilitating repair and replacement of parts.

An additional advantage lies in the fact that no sliding or slippingmovement between the pistons and/or piston shoes relative to thereaction ring is experienced, all relative movements being effectedthrough bearing linkages between the link arms and the piston andreaction ring.

As will be more fully appreciated in connection with the detaileddescription of the device, the radial movement of the pistons is adouble harmonic function, resulting from the superimposition of themovement imparted to the piston by the pivoting of the links about thereaction ring on the harmonic (sine) function generated by the rotationof the reaction ring. As a result, the initial movements of the pistonsaway from the minimum displacement position and the final returnmovements of the pistons to the minimum displacement positions are moregradually accomplished than would be the case if the pistons werecontrolled solely by a conventional reaction ring. This phenomenonresults from the fact that the pivotal movement of the parallel linksexerts a subtractive influence as respects the direction of movementimparted to the piston by the reaction ring assembly as the pistonsleave and approach the minimum displacement positions.

Accordingly, it is an object of the invention to provide an improvedradial piston pump or motor.

A further object of the invention is to provide a device of the typedescribed in which there is no tendency for the piston to cock relativeto the cylinder bores.

Still a further object of the invention is the provision of a radialpiston pump or motor wherein the connection between the pistons and thereaction ring is effected through a parallelogram linkage connectormeans which maintains the piston axis parallel with the cylinder axisand channels all forces exerted between piston and reaction ring in suchparallel directions.

Still a further object of the invention is the provision of a device ofthe class described and including an auxil-. iary piston stabilizerwhich absorbs, externally of the piston and cylinder, any side thrustforces exerted against the pistons.

Still a further object of the invention is to provide, in a device ofthe class described, a piston head which employs piston rings.

To obtain these objects and such further objects as may appear herein orbe hereinafter pointed out, reference is made to the accompanyingdrawings, forming a part hereof, in which:

FIG. 1 is a vertical sectional view through a radial piston pump ormotor in accordance with the invention;

FIG. 2 is a magnified section taken on the line 22 of FIG. 1;

FIG. 3 is a magnified vertical section through an embodiment of theinvention;

FIG. 4 is a section taken on the line 44 of FIG. 3;

FIG. 5 is a magnified section taken on the line 5-5 of FIG. 3.

Referring now to the drawings, there is shown in FIGS. 1 and 2 a radialpiston hydraulic pump-motor which comprises the usual pintle shaftcarrying a rotatable cylinder block assembly 11 in driving connectionwith;

an output or drive shaft 12. The apparatus carries, in addition, areaction ring chassis 13 which can, in the usual manner, be shifted fromside to side relative to the pintle shaft, namely, from left to right asviewed in FIG. 1, and toward and away from the viewer in FIG. 2.

It will be appreciated that, as in the usual radial hy draulic pump ormotor, some mechanical linkage (not shown) is connected to the reactionring chassis 13 through a manual or servo-mechanism, to control itsposition and, hence, the degree and sense of eccentricity of thereaction ring relative to the pintle shaft.

Typically, the reaction ring chassis position may be varied to locatethe axis of the reaction ring to either side or coaxial of the axis ofthe pintle shaft selectively, in accordance with the desired operationof the apparatus. The reaction ring chassis includes spaced supportdisks 14, 15, providing laterally elongated clearance spaces 16, 17,respectively, for effecting the desired eccentricity. The disks 14, 15are joined by the usual yoke or like assembly (not shown), forming apart of the mechanical linkage, to permit their simultaneous lateralmovement to effect the reaction ring eccentricity referred to above.

The peripheries 18, 19 of the disks 14, 15 form bearing races for thesupport of cylindrical bearing members 20, 21, or like bearingassemblies, the opposite races for the bearings being for-med in thereaction rings 22, 23, respectively.

In the usual manner, the block 11 includes a central bearing portion 24which is rotatably mounted about the pintle shaft 10. The pintle shaftincorporates high and low pressure conduits 25, 26, terminating inpressure distribution chambers 27, 28. It will be appreciated that thedistribution chambers 27, 28 are outwardly open, the chambers beingseparated by divider lands 29, 30.

The cylinder block includes a multiplicity of radially directedcylindrical structures 31, seven being shown in the illustratedembodiment. The cylinders 31 are provided with internal bores 32, theradial innermost ends of the bores incorporating fiuid distributionpassages 33.

Optionally but preferably, the passages are shaped in the manner shownin my US. Pat. No. 3,345,916 of Oct. 10, 1967, being axially elongatedin the direction of the pintle shaft and angularly reduced in size inthe areas adjacent said shaft, the passages progressively becoming widerand shorter as they merge with the cylinder bores 32. It will beunderstood that the inner terminal ends of the fluid passages aresequentially connected to the radially open high and low pressuredistribution chambers 27, 28 of the pintle shaft as the block rotates,the land areas 29, 30 being of a sufiicient angular extent completely toseal with a minimum of overlap each of the passages as they scan theland areas.

Within each of the bores there is mounted for recipro cation a pistonassembly including a piston head portion 34 in sealing relation of thebore and a piston rod 35 extending radially outwardly from the pistonhead. Adjacent their outermost ends 36, the piston rods 35 are formedwith a pair of bosses 37, 38, carrying cross rods 39, 40. The axes ofthe cross rods 39, 40 are equi-distant from the radius R of the pintleshaft when the pistons are in axial alignment within the bores 32 of thecylinders. The distal ends of the rods 39, 40 are provided with bearingstructures, such as roller bearings 41.

The outer race or component of each of the bearings 41 is afiixed to theoutermost end of a connector link 42a, 42b. In the illustrated device,four connector links are secured to each piston rod in view of the factthat the reaction rings proper are laterally offset from the axes of thecylinders. However, it will be appreciated from the description of thedevice that a single pair of link arms may be used to control the actionof the pistons, such an arrangement being appropriate where the reactionring is disposed in outward surrounding relation of the pistons.

The links 42a, 42b will hereafter be referred to as a pair of links, thetwo links on the opposite side of the block 11 and connected to theopposite reaction ring 22 also comprising a pair.

The opposite ends of the links are connected to hearing members 43supported on stub shafts 44 extending inwardly from the reaction rings22, 23. It is important that each pair of links 42a, 42b be mounted sothat the axis of the upper end of the links and the pivot axis of thelower ends of the links of each pair in all positions remain parallel toeach other and thus act in the manner of a parallelogram linkage.

From the foregoing description it will be apparent that by reason of theparallelogram linkages effected between the link pairs and the pistons,all forces transmitted by the pistons to the reaction ring or by thereaction ring to the pistons must be exerted against the pistons in adirection which is precisely in alignment with the longitudinal axes ofthe pistons and, hence, with the longitudinal axes of the cylinderbores.

By way of illustration, assuming the reaction ring chassis 13 to havebeen displaced to one side or another of the central position, thus tooffset the axis of rotation of the reaction rings 22, 23 from the radiusR of the pintle shaft, as shown in FIG. 1, if a torque is applied to theblock through the drive shaft 12 (thus using the apparatus as a pump),the block will rotate, carrying with it the reaction rings 22, 23. Asthe block rotates, the pistons are progressively reciprocated within thecylinders, developing a fluid pressurizing stroke toward the axis of thepintle shaft during one half of a rotation, and being refilled withhydraulic fluid from the low pressure distribution conduit 28 during theoutward movement of the pistons. In the course of the rotary movement,since all forces communicated from the reaction ring to the pistons arecommunicated through the parallelogram linkages, it is clear that thepiston axes are at all times maintained parallel with the axes of thecylinders. Therefore, any tendency of the pistons to cock or tilt withinthe cylinders is eliminated without the requirement of employingspherical or elongated pistons or similar disadvantageous expedients.

It will be observed that while moderate lateral forces between the sidesof the piston heads and the cylinder bores will be developed in thecourse of force transmission, such forces are nowhere near asdestructive as cocking forces which tend to tilt the pistons within thecylinders. The destructive nature of the cocking forces results frombringing relatively small areas of the pistons into contact with smallareas of the cylinders, the destructive effect being accelerated byreason of the fact that in conventional radial piston pumps and motorssuch forces are exerted through an extended moment arm by reason of thespacing of the pistons from the reaction ring.

As previously alluded to, many design and functional benefits may bederived from elimination of cocking or tilting forces to the piston.Specifically, since the piston head is not'relied upon as the primarymeans for stabilizing the piston within the cylinder, pistons withshorter heads may be effectively employed, without fear of scoring orinstability. The use of shorter head pistons brings secondary benefitsby way of facilitating lubrication, enabling increased displacement perover-all pump diameter, enabling a larger stroke per given pistonlength, and permitting the use of sealing mechanisms, such as pistonrings, between the piston head and the piston wall.

It will be further appreciated that, unlike conventional radial pistonpumps and motors in which a relative sliding action occurs between thepiston and/or piston shoe and the reaction ring, all of the thrustbetween these p rts is effected between the rotary bearing assemblies,such as the bearings 41 and 43.

In FIGS. 3 and 4 there is shown a further embodiment of the inventionwhich is calculated primarily to further reduce friction, being providedwith mechanism which relieves the piston head from the application oflateral forces exerted between the piston head and the cylinder bore. Inthis embodiment, wherein like parts have been given like referencenumerals, piston rod 35 is rigidly connected to a cross bar assembly 50,the cross bar or arm assembly being perpendicular to the axis ofcylinder bore 32. While the cross bar and piston rod may be integrallyformed, the connection is preferably effected through a threaded orotherwise secured inter-engaging 6 stud 51 on the piston, receivedwithin threaded aperture 52 on the assembly 50.

The pairs of connector arms 42a, 4211, with interposed bearing members,secure the cross bar assembly to the reaction rings in the mannerpreviously set forth, to assure the absence of any cocking forces.

The cylinder members 53 of this embodiment are formed with externalguide surfaces 54, 55 which parallel the cylinder axis. The cross arm 50is internally threaded, as at 56, and receives a guide cup 57, the upperend 58 of which is externally threaded and received within the portion56. The guide cup is threaded into the cross bar assembly 50, the cupincluding vertically directed, flattened guide surfaces 59, 60, disposedin parallel spaced relation to the surfaces 55, 54, respectively, on thecylinders. Sets of needle bearings 61, 62, diagrammatically illustrated,or other suitable anti-friction guides, are interposed between therespective surfaces 55, 59 and 54, 60, to provide a low friction guidingfunction between the cup 57 and the cylinder 53.

It will be observed that by reason of the parallel links connectionbetween the cross arm 50 and the reaction ring, there is no tiltingmoment applied to the guide cup 57. Thus, the bearing assemblies 61, 62are required to resist only lateral forces, which forces are dividedessentially equally among the bearing rollers of each race. In contrast,if the parallelogram linkage were not employed, it is evident that theconsiderable forces developed would be applied against an upper rollerof one bearing set and a lower roller of another.

Formed at the lower end of piston rod 35' is a piston head 65 which, asshown in FIG. 3, provides substantial clearances with respect to thecylinder walls. The piston head is provided with a series of spacedannular grooves 66, within which are mounted piston rings 67. The ringsprovide the requisite seals with respect to the cylinder bore 32'. Itwill be noted that, as in all devices incorporating piston rings, therings 67 permit a degree of lateral movement of the pistons in thecylinders, by reason of the clearances of the rings in grooves 66. Thepermitted lateral movement does not interfere with the proper operationof the illustrated device, however, since the piston head is not reliedon as a stabilizing element.

As best seen in FIGS. 4 and 5, the land area 29 separating the high andlow pressure areas of the pintle shaft may be provided withlongitudinally directed grooves G, the depth of which need not exceed afew thousandths of an inch. These grooves function to reduce leakageacross the outer surface of the lands between the lands and the rotatingblock, despite the existence of normal operating clearances. Withoutlimitation, it is believed that the reduction in leakage is a result ofan interruption of laminar flow across the face of the lands, thegrooves tending to induce a turbulence in any such laminar movement andthereby reducing leakage losses.

From the foregoing it will be appreciated that there is provided aradial piston pump and motor in which all forces exerted by or againstthe piston members are constrained to act in a direction which maintainsthe piston axis parallel with the cylinder axis. By this constructionnumerous advantages by way of reduced wear, greater design flexibility,increased stroke and reduced over-all size per given displacement areachieved. Additionally, there are no relatively movable slidingsurfaces, all hearings being of the low friction ball or roller bearingtypes.

Where the device is employed in connection with the external pistonstabilizer or guide, substantially all lateral forces are eliminatedbetween the piston head and the cylinder bore. Since the piston need nolonger function as a stabilizing mechanism, it is now possible to usepiston rings or like sealing mechanism, with their attendant economies.

No attempt has been made herein exhaustively to describe and explain allof the various design advantages and economies which may flow from theimproved construction here-0f.

The invention is to be broadly construed within the scope of theappended claim.

Having thus described the invention and illustrated its use, what isclaimed as new and is desired to be secured by Letters Patent is:

1. A radial piston pump or motor comprising a pintle shaft, a cylinderblock mounted on said shaft and including a plurality of radiallyextending cylinder members having internal cylinder bores and externalguide surfaces, said guide surfaces being disposed in a plane parallelwith said bores, a reaction ring assembly mounted for rotation about anaxis parallel with and displaced from the axis of said pintle shaft, apiston member mounted for reciprocation in each said bore, each saidmember including a head portion carrying piston rings in sealingrelation with said bore and a radially directed piston rod extendingoutwardly beyond the end of said cylinders, a cross arm assembly rigidlyafiixed to the outer end of each said piston rod including a spaced pairof bearing members having their axes disposed in a common plane normalto the axis of said cylinder bore, a pair of parallel links having firstend portions pivotally connected to said bearing members, the other endsof said links being pivotally connected to said reaction ring assemblywhereby said References Cited UNITED STATES PATENTS 2,001,706 5/1935Centervall 103-161 2,474,536 6/ 1949 Lundegard 103-161 2,510,247 6/ 1950Parenti 230-177 2,972,961 2/1961 Clark 103161 3,392,631 7/1968 Baker103161 FOREIGN PATENTS 267,102 8/ 1927 Great Britain. 686,067 12/ 1939Germany.

WILLIAM L. FREEH, Primary Examiner US. Cl. X.R. 9l180

